Condensed Consolidated Statements of Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Earned premiums, from affiliates	$ 55.7	$ 71.9	$ 168.5	$ 251.1
Net investment income, from affiliate	0.7	1.3	2.3	3.7
Losses and loss expenses, from affiliates	24.2	43.0	125.1	136.3
Net Acquisition and Operating Expenses, from affiliates	17.6	(26.8)	54.5	52.3
Interest Expense Debt To Affiliates	$ 0.2	$ 0.2	$ 0.7	$ 0.7